It is known in the art to which this invention pertains to provide upon steel, iron or related metal-bearing surfaces an electrodeposited essentially pure zinc coating for corrosion protection purposes. It is conventional in the electrochemical deposition of a zinc coating upon a steel substrate, subsequent to cleaning, rinsing and acid pickeling, to plate from a cyanide zinc bath, and after rinsing, to provide upon the zinc plated surface a passive film in the form of a chromate salt. This may of course take various forms, such as a clear-like coating which resembles nickel, or various textures and colors which assume the appearance of olive drab or colored zinc. However, experience has well indicated that under exposure to known salt spray and humidity environments, or to a locale in which there is a constant salt spray of high salt concentrations coupled with high humidity, the zinc layer under such conditions is penetrated into the steel substrate, and rust or other undesirable conditions are manifest. It has been proposed in order to overcome these difficulties that the zinc coating be increased in thickness; however, while a modest improvement has been noted in the area of corrosion protection, the final product obtained after relatively long exposure to an industrial or marine environment is generally not completely acceptable after lengthy service periods.